Dereck Chisora lit the touchpaper ahead of tomorrow's WBC heavyweight title challenge by slapping champion Vitali Klitschko at today's weigh-in in Munich.
The eccentric Londoner is a rank outsider ahead of the weekend's bout and attempted to get under the long-reigning champion's skin this afternoon.
After weighing in at 17 stone 3lbs - just a pound heavier than his lightest weight for a professional bout - Chisora butted heads before slapping Klitschko's face hard.
The two men were pulled apart, with a furious-looking Klitschko, who had weighed in three pounds heavier, left with a red mark on the left side of his face.
Chisora's camp said they were unaware of the stunt beforehand, with trainer Don Charles even branding the slap "unacceptable".
An angry Charles said: "It was unacceptable."
Asked whether it was pre-meditated, the trainer added: "I'm not Dereck Chisora. Like I said, it's unacceptable."
Promoter Francis Warren, representing his father Frank's company, said: "We're all scratching our heads about it, to be honest.
"You always expect something from Dereck - he's a character. But it's usually something that winds people up or is a bit jovial.
"So for him to get physical and aggressive, unprovoked, is surprising. But at the end of the day I'm sure there's method to his madness and we'll find out if the madness has paid off tomorrow night."
Warren added: "I was very surprised (by the slap) though. I wasn't expecting it at all.
"I don't think anybody wants to see that but it's happened now, so we'll move on and look forward to tomorrow night."
Asked whether he expects sanctions against Chisora, Warren said: "That's up to the governing bodies to decide. If there are sanctions then I suppose we will find out in the next couple of weeks.
"I'll sit down and have a chat with Dereck about it but at the moment we're focused on tomorrow night.
"Dereck is obviously a fiery character and that has got him to where he is. He can react like that to situations but at the end of the day he is a boxer, a fighter. Let's focus on the fight."
The 28-year-old Londoner challenges Klitschko in Germany despite two high-profile losses in his last three fights.
Despite being a relative novice, Chisora has already seen two clashes with Klitschko's brother Wladimir scuppered by the Ukrainian's injury withdrawals.
He was scheduled to fight the 35-year-old for the IBF and WBO belts in December 2010 before a stomach injury forced the champion to pull out and the rescheduled bout in April last year also fell through with Klitschko blaming a problematic rehabilitation.
While Wladimir went on to beat David Haye instead, Chisora remained at domestic level and lost his British and Commonwealth titles to Tyson Fury. Though he went some way to redeeming himself with a career-best performance against Finnish star Robert Helenius before Christmas, a controversial split decision ultimately saw him suffer a second career defeat.
The Zimbabwe-born Briton therefore takes on long-reigning heavyweight king Klitschko as a huge outsider, with some bookmakers pricing him as generously as 10-1 to dethrone the champion in his adopted homeland.
"I'm the underdog in this fight which is exactly how I like it because when I knock him out in the eighth round it will shock the world," said Chisora, who has a record of 15-2 (9KOs) and is ranked 14th by the WBC.
"I know I've got to go in there and do a job on him.
"I'm in tip-top condition and the best shape I've been in in my entire career, so I'm confident I'm going to smash Mr Vitali Klitschko to bits.
"I'm going to war with him. I'll make sure that he won't get to use his big height and reach advantage against me with the way I'm going to fight him and I've got the eighth round in my head that I'm going to stop him in."
Klitschko had spent the build-up to the fight talking up Chisora's credentials, citing his performance against Helenius in Finland in December as proof of his credentials.
"He's the strongest challenger out there and I always want to prove myself against the best," insisted the 40-year-old (43-2, 40KOs) this week.
"He is young, wild, aggressive and hungry. He marches forward all the time. The fight will be interesting."